Much recent attention has been paid in the technical and patent literature to the delivery of substances, both pharmaceuticals and cosmetics, such as drugs and other beneficial agents, into patients by passive processes such as diffusion and osmosis and by active processes such as electrically induced iontophoresis, electrophoresis, electroosmosis and/or electroporation. Hereinafter, the term “iontophoresis” will collectively represent any of the terms iontophoresis, electrophoresis, electroosmosis and/or electroporation; and the term “iontophoretic” will encompass the respective adjectives. The ubiquitous nicotine patch designed to assist in quitting smoking has caused such forms of delivery of medication to be widely known. Indeed, there is now an extremely long list of pharmaceutical substances that are routinely administered transdermally and a similarly long list of devices and methods known in the art for administering same. A short but varied sampling includes the following: U.S. Pat. No. 6,294,582 which discloses a device for treating asthma transdermally; U.S. Pat. No. 5,899,856 which discloses a dermal patch for detecting alcohol consumption; U.S. Pat. No. 6,291,677 which teaches the transdermal administration of antiviral protease inhibitors; U.S. Pat. No. 6,266,560 which discloses the transdermal treatment of erectile dysfunction; U.S. Pat. No. 6,238,381 which discloses the transdermal delivery of antiviral, antibacterial and antiaging substances; and U.S. Pat. No. 6,288,104 which discloses the transdermal administration of substances for treating congestive heart failure.
Most present dermal patches, including those that function passively and those that function electrically, incorporate an active substance to be delivered. Such patches are specifically designed and/or configured to deliver a predetermined dosage of a specific substance, and that substance forms an integral part of the patch in question, i.e., the “nicotine patch”. One drawback of such dermal patches, which are manufactured with a predetermined type and amount of substance therein, is that once the substance is depleted, the entire device is useless and must be discarded. This is a disadvantage because patches which employ electrically induced delivery techniques necessarily have components, e.g., batteries, electrodes, circuitry and other assemblies, which may be expensive and/or environmentally hazardous when discarded in large quantities. Also, in order to change dosage, patches of different dosages must be provided.
In iontophoresis, an electric current is used to drive ions of an active substance into or through the skin of a subject. Devices that deliver active substances using iontophoresis have been developed for many applications, most of which involve the delivery of pharmaceutical compounds through the subject's skin and into the circulatory system or other organs of a subject's body. Topical application of one or more active ingredient to the skin through the use of an iontophoresis device is called dermal treatment. Iontophoretic devices have taken two basic forms:
First, there are flexible, wearable devices such as transdermal patches. Most such devices include a small power source (such as an electrochemical cell), an electrode for delivering the active substance (i.e., a dispersing electrode), another electrode, and circuitry providing a small current through the electrodes and into the skin of the subject's tissue to be treated. The circuit is closed by contact with the subject's skin.
An advantage of such devices is their convenience. For example, with a transdermal patch, a subject can move around while still using the patch, and can use the patch at home. A drawback of such devices is that unless expensive and potentially bulky control elements are included, there is limited control over the delivery of the active substance, including the depth to which the active substance is delivered into the subject. This is not as important when delivery of pharmaceutical compounds is involved, since the object is generally to deliver the active substance through the skin and into the rest of the subject's body. However, precise depth control is more important for delivery of compounds used for cosmetic or dermatological applications, as the object is to deliver the active substance into the skin, but not through the skin.
The second basic form of iontophoretic devices are machines that include a separate base unit to which rigid electrodes are attached by cables. These machines are stationary, and are plugged into an electrical outlet. In operation, the electrodes connected to these machines are placed on the skin, which results in delivery of the active substance according to the same principles discussed above.
An advantage of these machines is that they may allow for some control of the delivery of the active substance by adjusting the parameters of the machine while it is in operation. For example, the rate of delivery could be increased by increasing the current density supplied by the machine. A drawback of such machines is that they are relatively inconvenient. The subject cannot move around while using such machines. Moreover, due to the cost of the machines, they generally cannot be used at home, but instead can only be used at a medical facility (for machines that deliver pharmaceutical compounds) or spa or beauty parlor (for machines that deliver cosmetics).
Another drawback of these machines is that the entire active electrode is not in contact with the subject's skin, which can result in varying amounts of active substance being delivered at different locations along the skin/electrode interface (e.g., greater amounts of active substance are delivered at those skin locations on the interface that are in contact with the active electrode for the greatest amount of time). This phenomenon is exacerbated in machines of this basic form that are used to deliver cosmetics by iontophoresis. An example of such a machine is the IONZYME™ DF 1998. Such machines may have the active electrode attached to a roller that is rolled back and forth over the skin of a subject, delivering dermatological and/or cosmetic ingredients at the momentary point of contact of those rollers with the skin.
Thus, there is a need for a thin, flexible and simple electrically active dermal patch that is easy to administer by the subject, versatile and capable of application with a range of substances and/or dosages and for a variety of purposes and that is simple in design and inexpensive to manufacture. There is also a need for a device, which is flexible and wearable on the one hand, but on the other hand allows for a uniform and precise depth control without the inclusion of an additional control element. Such a device would facilitate the delivery of active substances (such as cosmetics) that are most effective when delivered into the skin with minimal delivery through the skin, without sacrificing the basic convenience of a transdermal patch.